We will build a peptide "printer" capable of putting 10,000 different peptides on a 35 mm "chip." To achieve this, we will synthesize each peptide in situ on the chip, printing each successive amino acid of each peptide. MicroFab's fast, multichannel printers can print 10,000 amino acid spots in under 30 minutes. Wash, rinse, deprotect, and coupling cycles might consume 30 minutes, yielding a synthesis rate of 1 hr/residue. An array of 10,000 different fifteen-mers could be synthesized in under 24hr. In Phase I we will prove the principle by printing amino acid microspots, verifying substrates and attachment chemistry, and synthesizing and verifying a peptide. In Phase II we will build a prototype printer capable of making 1534 peptide "chips." Peptide vaccines and peptide drugs are rapidly becoming tools of choice for prevention and treatment of infections disease. These efforts are rat- limited by the task (and cost) of synthesizing peptides for screening. Our peptide chips can lower the cost and the time of large scale peptide screening by at least 1-fold and probably 100-fold. Peptide are a $1 billion/yr business; 1% of the market would be a substantial business. PROPOSED COMMERCIAL APPLICATIONS: High-throughput screening for vaccine-candidate epitopes, for peptide drugs, or for expressed proteins (by peptide capture) all require a massively parallel, peptide-chip based approach. Our system can be first- to-market and thus capture the bulk of that market.